<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>

<canvas id="myCanvas" width="200" height="100"></canvas>

<script type="text/javascript">
  var c = document.getElementById("myCanvas");
  var cxt = c.getContext("2d");
  cxt.fillStyle = "#FF0000";
  cxt.fillRect(0,0,150,75);
</script>

</body>
</html>